Make Palmer Indices ready to use for research

[lukruh]

Hello,
it's written in the disclaimer, that the Palmer indices are not ready to use for research. Also I found a few open issues regarding to the implementation of the palmer indices. I've read the palmer and wells papers and can see that it's not just a trivial equation to implement, but I wonder what the specific tasks would look like to make this ready to be used for research.
I'm not an expert on palmers indices, but I've worked with drought indices before and would prefer to work on the index implementation in this library rather than switching to another existing library (i.e. scPDSI in R). If there is any chance to get this done in the near future.

[monocongo]

I attempted to update the suite of Palmers used at NOAA and this is the result. It was never fully vetted and in a few cases it gets different results than the Fortran (pdi.f) etc. used at NOAA. The experts on the Palmer indices are few and far between, and I saw little enthusiasm for coalescing on a community-accepted implementation or even a golden result set, instead everyone just rolls their own and calls it good. If someone can put a better implementation together then such a contribution is very welcome here. It seems like a golden opportunity for someone in climate science to put out a rock-solid implementation that can be easily used by others while at the same time exhaustively reviewed and developed collaboratively due to it being open source. Hopefully, this package can provide a start for that, but getting to that goal has eluded me so far, hence the warning off from the usage of the Palmers for proper research.